Insertable medical devices used as vascular supports (i.e., stents) or filters have been used in various medical procedures, such as in angioplasty. An example of an intravascular radially expandable stent used in angioplasty is described in U.S. Pat. No. 4,886,062 issued to Wiktor on Dec. 12, 1989. This device includes a wire winding having the shape of a helical spring, see the front page drawing. U.S. Pat. No. 3,868,956 issued to Alfidi et al. on Mar. 4, 1975 shows a vessel implantable device made of a biocompatible shape memory nickel-titanium alloy wire (i.e., Nitinol wire).
In particular, biomedical filters are implanted in veins to capture emboli or thrombi. For example, prior to surgery, a filter can be implanted into the inferior vena cava to protect the heart and lungs from clots. US Published Application No. 2008/0027481 filed by Gilson et al., published Jan. 31, 2008 describes a generally conically shaped vascular filter that appears to include a Nitinol frame structure with at least a portion of it including bioabsorbable material, see paragraphs 27-33. The filter can include barbs, see 302, FIGS. 26(a) and (b). The filter catches thromboemboli in the inferior vena cava as the blood travels toward the heart and lungs.
International patent application WO2007/079413 (Kashkarov et al.) describes an embolus blood clot filter with bio-resorbable coated filter members, see front page drawing, having a structure generally corresponding to current description, including bioabsorbable portions extending from substrate structure (e.g., Nitinol substrate). However, this document appears to be silent regarding gradually thickening bioabsorbable and/or bioactive prong elements as in the present inventive device.
U.S. Pat. No. 6,972,025 issued to WasDyke on Dec. 6, 2005 describes an intravascular filter with a bioabsorbable centering element, see abstract. Similarly, see U.S. Pat. No. 7,491,215 issued to Vale et al.
U.S. Pat. No. 7,347,869 issued to Hojeibane et al. on Mar. 25, 2008 describes an implantable valvular prosthesis including Nitinol and bioabsorbable material. However, this document appears to be silent regarding the particular relationship of the bioabsorbable extensions of the barbs and filter structure that are attached to the Nitinol portions.
U.S. Pat. No. 7,229,471 issued to Gale et al. on Jun. 12, 2007 describes compositions containing fast-leaching plasticizers for use in medical devices, e.g., bioabsorbable materials. However, this document appears to be silent regarding the particular filter and/or stent structure.
U.S. Pat. No. 5,569,295 issued to Lam on Oct. 29, 1996 describes expandable stents that include superelastic NiTi alloys (column 7, second full paragraph) and use of bioabsorbable adhesives, column 2, lines 44-47.
US Patent Application No. 2008/0281350 filed by Srpetka et al. describes aneurysm occluding devices using a biocompatible matrix, including shape memory plastics.
U.S. Pat. No. 4,425,908 issued to Simon on Jan. 17, 1984 describes a blood clot filter placeable in a vein, e.g., vena cava, including Nitinol wires, see passage in document under “Detailed Description”. However, this document appears to be silent regarding the use of varying-thickness bioabsorbable material and the structure of the present inventive device.
U.S. Pat. No. 7,498,385 issued to Swetlin et al. describes a polyester composition that can be used to make a biocompatible stent or other biomedical structure.
US Patent Application No. 2007/0250158 to Krivoruchko et al. describes a laminated stent including a metal coating, see the abstract. Also, related WO 2007127541.
US Patent Application No. 2008/0015683 to Kramer-Brown describes a stent made of cobalt chromium alloy.
US Patent Application No. 2007/0219626 to Rolando describes a stent including bioabsorbable material.
However, it is noted that none of the documents uncovered and cited below appear to describe the combination of the Nitinol ring-frame substrate with gradually thickening prong extensions and the bioabsorbable extensions on the Nitinol prongs as described herein.
The cited documents all appear to be directed to devices and structures that can be placed in anatomic vessels, e.g., veins and arteries, and which have either shape memory (e.g., cobalt chromium), metal or nonmetal coating, and/or bioabsorbable features, or general arrangements for applying a coating onto a medical device that corresponds to the inventive filter or stent device.
However, none of the known structures provide a structure that controls the rate of release of a bioactive material after implantation of the device, e.g., by catheter, in a predetermined manner using a plurality of conically shaped bioabsorbable prongs as herein described.
Therefore, there is a need for an implantable vascular medical device in which a bioactive substance, e.g., heparin or other anti-platelet drug, etc., is released at a predetermined, controlled, varying rate after implantation, that is based on the particular needs of a patient. This is achieved in the inventive device by the particular construction of bioabsorbable prongs containing the bioactive material, with optional additional coatings, on an expandable wire frame that includes an undulating ring core and a plurality of transversely attached wire segments. The wire frame can be Nitinol or any other biocompatible shape-memory metal or alloy material, or a comparable biocompatible polymer shape-memory material.